Solid Electrolytic Capacitor and Improved Method for Manufacturing a Solid Electrolytic Capacitor

ABSTRACT

An improved process for forming a capacitor, and improved capacitor formed thereby is described. The process includes:
     providing an anode comprising a dielectric thereon;   applying a first layer of an intrinsically conducting polymer on the dielectric to form a capacitor precursor;   applying at least one subsequent layer of an intrinsically conducting polymer on the first layer from a dispersion; and   treating the capacitor precursor at a temperature of at least 50° C. no more than 200° C. at a relative humidity of at least 25% up to 100%,   or fusing the layered structure by swelling the layered structure with a liquid and at least partially removing the liquid.

BACKGROUND

The present invention is related to an improved solid electrolyticcapacitor and an improved method of manufacturing a solid electrolyticcapacitor. More specifically, the present invention is related to animproved treatment method which provides for improvements in the coatingquality and physical properties of the finished capacitor.

Solid electrolytic capacitors have been widely used for many yearsthroughout the industry. Of particular interest herein is a solidelectrolytic capacitor comprising a cathode of an intrinsicallyconducting polymer such as polyaniline, polythiophene or polypyrroles.The polymers are usually either formed in-situ or by dipping into aslurry of polymer. With in-situ formation a capacitor precursor isintroduced into a monomer solution wherein the monomer is polymerizedeither electrochemically or by chemical means.

It is well known in the art that when forming a coating from polymerslurry achieving an adequate coating on the edges and corners is verydifficult. The slurry tends to pull away from the edges and corners,believed to be due to surface tension driven capillary effects. Theresult is thin layers and, in some cases, voids or holes within thecoating, which is detrimental to achieving a high quality capacitor. Oneof skill in the art typically applies multiple layers, beyond thoseneeded for capacitance, to insure adequate coverage of the edges andcorners.

Efforts to mitigate edge and corner thinning are described throughoutthe literature as exemplified in U.S. Pat. Publ. No. 2012/0057275wherein cross-linkers comprising at least one diamine, triamine,oligamine or polymeric amine is applied before the application of thepolymer slurry. While advantageous, the use of strong ionic acid anionswith the cross-linking technology has now been understood to bedetrimental due to corrosion of the underlying anode. This is aparticular problem with an aluminum anode wherein the corrosion occursrapidly.

Yet another problem with the cross-linkers is that each slurry layertends to dry and form a skin. Subsequent layers then do not adequatelymigrate through the skin into previous layers and the layers are joinedby adhesion not cohesion. The result is the formation of a cathodewherein discrete layers separate, or delaminate, under harsh conditionsthereby decreasing conductivity between adjacent layers and increasingequivalent series resistance (ESR). The stability and reliability ofcapacitors made with the layered coating of conductive polymer is alsoundesirable.

In spite of the advances made in the art there is still a significantneed for capacitors which maintain their properties in adverseconditions without loss of capacitance due to anode corrosion or anincrease in ESR due to cathode degradation and layer separation.

SUMMARY

It is an object of the invention to provide an improved capacitor, andparticularly capacitors which are not detrimentally impacted by adverseconditions with regards to capacitance or ESR performance.

It is another object of the invention to provide an improved method ofmanufacturing a capacitor which provides for adequate edge and cornercoverage yet does not detrimentally impact the properties of thecapacitor, such as capacitance and ESR, under adverse environmentalconditions.

These and other advantages, as will be realized, are provided in aprocess for forming a capacitor comprising:

providing an anode comprising a dielectric thereon;applying a first layer of an intrinsically conducting polymer on thedielectric to form a capacitor precursor;applying at least one subsequent layer of an intrinsically conductingpolymer on the first layer from a dispersion; andtreating the capacitor precursor at a temperature of at least 50° C. nomore than 200° C. at a relative humidity of at least 25% up to 100%.

Yet another embodiment is provided in a process for forming a capacitorcomprising:

providing an anode comprising a dielectric thereon;applying a first layer of an intrinsically conducting polymer on thedielectric to form a capacitor precursor;applying at least one subsequent layer of an intrinsically conductingpolymer on the first layer from a dispersion thereby forming a layeredstructure;fusing the layered structure by swelling the layered structure with aliquid and at least partially removing the liquid.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a cross-sectional schematic view of an embodiment of theinvention.

FIG. 2 is a cross-sectional schematic partially-exploded view of anembodiment of the invention.

FIG. 3 is a flow chart representation of an embodiment of the invention.

FIG. 4 is a cross-sectional view of a cathode layer without inventivetreatment.

FIG. 5 is a cross-sectional view of a cathode layer with inventivetreatment.

DESCRIPTION

The present invention is directed to an improved capacitor and improvedmethod of making a capacitor, particularly a solid electrolyticcapacitor comprising intrinsically conductive polymer, with improvedstability under adverse and processing conditions. More specifically,the present invention provides a method of fusing conductive polymerlayers by using high temperature and high humidity treatment, by soakingthe layered structure in a liquid or solution, or by vapor treatmentwith some selected liquid that helps to swell and fuse the distinctivelayers. This improves the bonding between adjacent layers ofintrinsically conductive polymer

The invention will be described with reference to the figures which forman integral, non-limiting component of the disclosure. Throughout thedisclosure similar elements will be numbered accordingly.

An embodiment of the invention is illustrated in schematiccross-sectional view in FIG. 1. In FIG. 1, a capacitor, generallyrepresented at 10, comprises an anode, 12, with an anode wire, 14,extending therefrom. A dielectric, 16, is on the anode at leastpartially encasing the anode. A conductive polymeric cathode, 18, is onthe dielectric and separated from the anode by the dielectric. Adhesionlayers, 20, provide a layer which allows adhesion to a cathode externaltermination, 22. An anode external termination, 24, is in electricalcontact with the anode wire. The entire capacitor, except for the lowerportion of the anode and cathode external terminations, is preferablyencased in a non-conductive matrix, 26, or sealed in a hermeticallysealed container as known in the art.

An embodiment of the invention is illustrated in FIG. 2 wherein acapacitor is generally represented at 110. A series of anodes, 120, arearranged in parallel fashion. Each anode has a dielectric, 116, thereon.A conductive polymer cathode, 118, is on each dielectric. The anodes arefused at 123 and the cathodes are commonly terminated.

The present invention provides a method for fusing conductive polymerlayers by using high temperature and high humidity treatment, by soakingthe layered structure in a liquid or solution, or by vapor treatmentwith some selected liquid that helps to swell and fuse the distinctivelayers. This improves the bonding between adjacent layers ofintrinsically conductive polymer and results in improved ESR and ESRstability.

An embodiment of the invention is illustrated in flow-chart form in FIG.3. In FIG. 3, an anode is provided at 30. A dielectric is formed on theanode at 32. An initial coating of primer is applied at 34 followed bycoating with a conductive polymer, preferably as a slurry, at 36.Subsequent layers are applied at 38. At least two polymer coatings areapplied with the number based on the desired thickness and completenessof coverage. A particularly preferred conductive polymer is poly3,4-ethylenedioxythiophene (PEDT). PEDT slurry is commercially availablefrom Heraeus as Clevios® KV2. The layers are dried and then fused at 40,preferably, at a temperature of at least 50° C. to no more than 200° C.and a relative humidity of at least 25-100%. More preferably thetemperature is at least 115° C. to no more than 130° C. More preferablythe relative humidity is at least 75%. Once the desired thickness andcoverage of conductive polymer is achieved the capacitor is finished at42 by forming anodic and cathode external terminations and optionallyencapsulating or sealing the capacitor.

While not limited to any theory, it is hypothesized that the moistureswells the layers and that upon heating the layers are more intimatelybound or fused to form a more homogenous coating with indistinguishablestriations.

In another embodiment the layered structure can be treated with aliquid, preferably a polar liquid, which enhances the swelling.Particularly preferred liquids for swelling the layered structureincludes water, ethylene glycol, propylene glycol, glycerol, dimethylsulfoxide (DMSO), N-methyl pyrrolidone or N, N-dimethylformamide (DMF).Treatment is preferably done by dipping due to the manufacturingefficiency provided thereby with other techniques, such as spraying,suitable for demonstration of the invention. After sufficient treatmentto achieve swelling the liquid is removed by either reduced pressure,increased temperature or some combination thereof at a rate sufficientto avoid surface drying or skinning. The temperature is preferably nomore than the boiling point of the liquid even though this temperaturecan be exceeded if surface drying is not caused by the more rapid liquidremoval. Temperatures of 25° C. to 150° C. are suitable fordemonstration of the invention with glycerol.

In yet another embodiment the layered structure can be treated with anaqueous or nonaqueous solution of a chemical that can help to swell thelayered structure. Particularly preferred solvents include water;alcohol such as ethanol or isopropanol; ketones such as acetone ormethyl ethyl ketone; ethers; esters such as ethyl acetate or isoamylacetate or ring based polar solvents such as tetrahydrofurane (THF).Suitable solutes include any compound that helps to swell the layeredstructure. In addition to the polar liquid mentioned in the aboveembodiment, particularly preferred solutes also include polar solidcompounds such as polyols including sorbitol, mannitol, sucrose andlactose and amino acids including glycine, alanine and lysine. Treatmentis preferably done by dipping due to the manufacturing efficiencyprovided thereby with other techniques, such as spraying, suitable fordemonstration of the invention. After sufficient treatment to achieveswelling the parts are dried to at least partially remove the solvent byeither reduced pressure, increased temperature or some combinationthereof at a rate sufficient to avoid surface drying or skinning. Thetemperature is preferably no more than the boiling point of the liquideven though this temperature can be exceeded if surface drying is notcaused by the more rapid liquid removal. Temperatures of 25° C. to 150°C. are suitable for demonstration of the invention with aqueoussolution.

In yet another embodiment layered structure can be treated with vapor ofany liquid or solute mentioned in the above embodiment. Heat can beoptionally applied to speed up the swelling and fusing of conductivepolymer layers.

The primer preferably comprises a cross-linker and a weak ionic acidcounter-ion.

The weak ionic acid counterion preferably comprising multiple carboxylicacid groups and has a preferred pKa of at least 0.25 to no more thanabout 6. More preferably the weak ionic acid counterion has a pKa of atleast 2.15 to no more than about 6. Below a pKa of about 0.25 thefinished part fails in accelerated reliability test. Above a pKa ofabout 6 the ionic acid is insufficiently ionic to function as a suitablecounterion. Acids containing multiple carboxyl groups on a linear orbranched hydrocarbon of at least one to 20 carbons, are particularlypreferred. Above about 20 carbons the solubility of the weak ionic acidcounterion becomes limiting. A particularly preferred weak ionic acidcounterion is selected from the group consisting of acetic acid,1,2,3,4-butanetetracarboxylic acid, lysine and butanetetraacetic acid

Typical primers, particularly, and cross-linkers are known to bedetrimentally impacted by moisture due, presumably, to their ionicnature. Aluminum is particularly known to be detrimentally impacted bythe presence of moisture. It has therefore been considered necessary toavoid high moisture conditions during the manufacture of capacitorsutilizing intrinsically conducting polymer due to the presence of theprimers specifically. In a surprising development, the use of relativelyhigh moisture and heat, as set forth elsewhere herein, fuses adjacentlayers of the intrinsically conductive polymer thereby achievingsuperior properties, particularly ESR, of the resultant capacitor. Thisresult is contrary to the expectation of those of skill in the art. Thesurprising realization that moist heat improves inter-layer bondingwithin the layers of intrinsically conducting polymer allows for the useof previously unsuitable weak counter ions thereby greatly improving thereliability characteristics of the capacitor. The result is a capacitorwith improved stability upon aging and subsequent use.

The cross-linker is preferably a diamine, triamine, oligoamine orderivatives thereof wherein oligoamine refers to compounds comprising atleast four amine groups such as tetramine, pentamine, hexamine,heptamine, octamine, nonamine, decamine, undecamine, dodecamine, etc.Particularly preferred amines are selected from aliphatic amines,amides, aromatic amines, amino acids, polymeric amines, and polyetheramines.

Aliphatic amines including α,ω-diamines such as 1,4-diaminocyclohexaneor 1,4-bis aminomethyl(cyclohexane), or

linear aliphatic α,ω-diamines or derivatives thereof such asethylenediamine, 1,6-hexanediamine, 1,7-heptanediamine,1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine or1,12-dodecanediamine N,N-dimethylethylenediamine,N,N,N′N′tetramethyl-1,4,butanediamine,N,N,N,N′N′N;-hexamethylhexanemethylene-diammonium dibromide, piperazine,1,4-diazabicyclo[2.2.2]octane,N,N,N′N-tetrakis(2-hydroxypropyl)ethylenediamine,N-[3-(trimethoxysilyl)propyl]ethylenediamine or1,4-bis(3-amino-propyl)piperazine; amides such asN,N′-diacetyl-1,6-hexanediamine, N,N,N′N′-tetraacetylethylene-diamine,1,4-diformylpiperazines or N,N′-ethylenebis(stearamide); aliphaticamines, including linear aliphatic amines, having at least three aminogroups such as 1,4-bis(3-aminopropyl)piperazine,N-(6-aminohexyl)-1,6-diaminohexane orN-(3-aminopropyl)-1,4-diaminobutane or3-[2-(2-aminoethylamino)ethyleneamino]propyltrimethoxysilane; aromaticamines having at least two amino groups such as brilliant green,4,4′-methylenebis(N,N-diglycidylaniline), o-phenylene-di-amine,m-phenylenediamine, p-phenylenediamine, 1,5-diaminonaphthalene,1,8-diaminonaphthalene, 2,3-diaminonaphthalene, 3-aminophenyl sulfone,4-aminophenyl sulfone, 4-aminophenyl ether, 3-3′-diaminobenzidine,2-(4-aminophenyl)ethylamine, 4,4′-methylenendianiline,2,6-diamiotoluene, N,N,N′N′-tetramethyl-p-phenylenediamine,4,4′-bis(diethylamino)benzophenone, 4,4′-bis(dimethyl-amino)benzhydrol,3,3′,5,5′-tetramethylbenzidine, Auramine O, Rubine S, m-xylenediamine,phthalein, complexone, Brilliant Blue G, folic acid; aromatic triaminessuch as 4,4′,4″-methyliditetris (N,N-dimethylaniline); polymeric aminessuch as poly(propylene glycol)bis(2-aminopropyl) ether,polyethyleneimine and poly(allylamine), ethoxylated polyethyleimine; andpolyethers such as NH₂—(CH₂)_(x)(CH₂CH₂O)_(y)(CH₂)_(z)—NH₂, wherein xand z are an integer from 0 to 3 and y is an integer from 2 to 8, andimidazole derivatives.

Solid electrolytic capacitors generally comprise a porous metal anode,an oxide layer on the anode, typically an oxide of the anode metal, andan electrically conductive solid cathode, such as manganese dioxide oran intrinsically conductive polymer, incorporated into the pores andonto the dielectric. The porous structure gives high surface area. Anadvantage of the high surface area is that a very high capacitance canbe achieved. Additional layers, such as silver and carbon layers, arethen added to aid in contact formation.

The solid electrolytic capacitors typically incorporate valve metals orconductive oxides of valve metals with tantalum, aluminum, niobium andniobium oxide being mentioned as particularly preferred.

The dielectric is typically formed as an oxide of the anode metalwithout limit thereto. Dielectric formation is well documented in theart and the method of dielectric formation is not limited herein.

Conductive polymers are particularly suitable for use as theelectrically conductive solid cathode with polyaniline, polypyrroles andpolythiophenes being most preferred. A particularly preferred polymerfor use as a cathode is polythiophene. The polymer layer inside thepores can be formed by chemical polymerization wherein the internalconductive layer is formed by dipping the anodized substrate first in asolution of monomer of the conductive polymer. After a drying step, theanode bodies are then immersed in a solution comprising oxidizer anddopant. The chemical polymerization cycle can be repeated multiple timesto achieve the desired coverage of the surface inside the pores. Thepolymer layer inside the pores can also be formed by dip coating using asolution or dispersion of conductive polymer. When a solution ofconductive polymer is utilized a diluted solution is preferred so thatthe solution viscosity would be sufficiently low to allow diffusion ofthe solution into the porous structure. In case of a dispersion of theconductive polymer the particle size must be sufficiently small to allowimpregnation of the porous structure.

A layer of conductive polymer can be applied with a slurry or dispersionof the conductive polymer. It is preferred to include a dopant in thepolymer as known in the art. A particularly preferred dopant is thesodium salt of polystyrenesulfonate (PSS) or polestersulfonate (PES).

The conducting polymer is preferably an intrinsically conducting polymercomprising repeating units of a monomer of Formula I:

R¹ and R² of Formula I are preferably chosen to prohibit polymerizationat the β-site of the ring. It is most preferred that only α-sitepolymerization be allowed to proceed. Therefore, it is preferred that R¹and R² are not hydrogen. More preferably R¹ and R² are α-directors.Therefore, ether linkages are preferable over alkyl linkages. It is mostpreferred that the groups are small to avoid steric interferences. Forthese reasons R¹ and R² taken together as —O—(CH₂)₂—O— is mostpreferred.

In Formula I, X is S, Se or N. Most preferably X is S.

R¹ and R² independently represent linear or branched C₁-C₁₆ alkyl orC₁-C₁₈ alkoxyalkyl; or are C₃-C₈ cycloalkyl, phenyl or benzyl which areunsubstituted or substituted by C₁-C₆ alkyl, C₁-C₆ alkoxy, halogen orOR₃; or R¹ and R² taken together, are linear C₁-C₆ alkylene which isunsubstituted or substituted by C₁-C₆ alkyl, C₁-C₆ alkoxy, halogen,C₃-C₈ cycloalkyl, phenyl, benzyl, C₁-C₄ alkylphenyl, alkoxyphenyl,halophenyl, C₁-C₄ alkylbenzyl, C₁-C₄ alkoxybenzyl or halobenzyl, 5-, 6-,or 7-membered heterocyclic structure containing two oxygen elements. R₃preferably represents hydrogen, linear or branched C₁-C₁₆ alkyl orC₁-C₁₈ alkoxyalkyl; or are C₃-C₈ cycloalkyl, phenyl or benzyl which areunsubstituted or substituted by C₁-C₆ alkyl.

More preferably R¹ and R² independently represent —CH₃, —CH₂CH₃; —OCH₃;—OCH₂CH₃ or most preferably R¹ and R² are taken together to represent—OCH₂CH₂O— wherein the hydrogen can be replaced with a solubilizinggroup, a halide or an alkyl.

A solvent is defined as a single solvent or a mixture of solvents.

It is preferable to apply the dispersion comprising the conductivepolymer at a pH of no more than 10 and more preferably no more than 8with below 7 being more preferred and below 6 being especiallypreferred.

The conductive polymer dispersion is applied onto the primer to form alayer that covers the edges and corners of the anodes. The applicationof primer layer and the conductive polymer layer can be repeatedmultiple times to achieve enough thickness and completeness of coverage.Without limit thereto 2-10 cycles of primer and conductive polymer layerapplication are suitable for demonstration of the invention. Eachapplication of conductive polymer may use a unique composition and aunique solution or an identical or similar material may be used for thevarious dipping steps. A preferred thickness of the conductive polymerlayer is at least 2 micrometers to no more than 50 micrometers. A morepreferred thickness of the conductive polymer layer is from at least 2micrometers to no more than 40 micrometers. An even more preferredthickness is from at least 3 micrometers to no more than 30 micrometers.If the layer of conductive polymer is below about 2 micrometers thedielectric is not adequately covered resulting in defective capacitors.If the conductive polymer layer is over about 50 micrometers theequivalent series resistance of the resulting capacitor is compromised.

In one embodiment a nanoparticle dispersion is applied after formationof the initial conductive polymer layer and after formation ofsubsequent conductive polymer layers. The sequence of applying thenanoparticle dispersion material followed by applying a conductivepolymer layer is repeated until the desired layer thickness is reached.Without limit thereto 2-10 cycles of the nanoparticle dispersion andconductive polymer layer application is suitable for demonstration ofthe invention. Nanoparticle dispersions comprise nanoparticles with thenanoparticles having a particle size of no more than 100 nm and morepreferably no more than 50 nm. Nanoparticles of the nanoparticledispersion are selected from aluminum oxide, zinc oxide, silicon oxideand cerium oxide. These nanoparticle dispersions are available from BykAdditives And Instruments under commercial name Nanobyk 3600 foraluminum oxide, Nanobyk 3810 for cerium oxide and Nanobyk 3820 for zincoxide.

HAST is Highly Accelerated Stress Test wherein a sample can be testedfor corrosion resistance under electrical bias at 121° C. and 85% RH.HAST testing typically requires about 1-200 hours. For the purposes ofthe instant disclosure b-HAST refers to a test under electrical bias andub-HAST is the same test without electrical bias.

A surprising result is presented in the present disclosure. When weakionic counter ions, as defined elsewhere herein, are utilized especiallywith the cross-linker the initial results are negative in that the ESRrises to an unacceptable level even though superior covering of thedielectric is observed. This has led to those of skill in the artavoiding weak counterions. It is surprisingly found that by theapplication of moist heat at a temperature and humidity as set forthelsewhere herein the ESR lowers to a level which is comparable to priorart wherein strong acid counter-ions are used. While not limited to thetheory, the improved treatment is thought to improve inter-layeradhesion. FIG. 4 illustrates a cross-sectional view of the intrinsicallyconducting polymeric cathode layer, coated using conventional Clevious®K Primer W, in a solid electrolytic capacitor treated by conventionaldrying techniques. Inter-layer striations are easily observed which arebelieved to separate upon aging. FIG. 5 illustrates an identicallyprepared layer treated at 121° C. in 85% relative humidity wherein thestriation is not observed and the intrinsically conductive polymer layerappears to be a continuous layer which does not as easily delaminateupon aging.

Moist heat, especially with aluminum, has long been considereddetrimental due to anode degradation. It is surprisingly found that withweak ionic counterions moist heat can be used, preferably with a postheating step, to provide an improved capacitor exhibiting relatively lowESR, good stability during manufacturing process and low leakage currentwith aluminum anodes as well as improved reliability. The anode does notsuffer from corrosion as is commonly realized with prior art strong acidcounterions. In yet another surprising result, when the inventivecapacitor is subsequently dried, the ESR and leakage current remain lowduring subsequent processing.

The unique combination of specifically selected weak ionic counterions,and specific processing conditions, provides a capacitor with a low ESR,uniform cathode deposition, minimal anode corrosion even under harshconditions and the ESR and leakage current remain low during subsequentprocessing. Such a combination of advantages is difficult to otherwiseachieve in the art.

Though not limited to theory, experimental evidence suggests that thecombination of the cross-linker and weak ionic counter ion react to forman uncharacterized product which improves adhesion, or cohesion, withinthe layer of the conductive polymer layer. Through designed experimentswith dodecylamine and butanetetracarboxylic acid following treatment asdescribed elsewhere herein a thermal analysis indicates meltingproperties which are not consistent with either the dodecylamine or thebutanetetracarboxylic acid.

EXAMPLES Test 1

A series of capacitors were formed on an aluminum anode with aluminumoxide dielectric. The dielectric was coated with a commerciallyavailable primer comprising dodecane diamine and toluene sulphonic acidavailable as Clevios® K Primer W from Heraeus. A layer of intrinsicallyconducting 3,4-ethylenedioxythiophene polymer available as Clevios® KV2from Heraeus was formed on the dried primer. The capacitor was testedfor ESR, the ratio of edge to body coating thickness and b-HAST. Theresults are presented in Table 1 as Comparative 1.

Test 2

A series of capacitors were formed on an aluminum anode with aluminumoxide dielectric. The dielectric was coated with a primer comprisingdodecane diamine and 1,2,3,4-butanetetracarboxylic acid in a 1:1 molarratio. Sequential layers of intrinsically conducting3,4-ethylenedioxythiophene polymer available as Clevios® KV2 fromHeraeus were formed on the dried primer. The capacitor was tested forESR, the ratio of edge to body coating thickness and b-HAST. The resultsare presented in Table 1 as Inventive 1.

TABLE 1 Sample Solid ESR (Ohms) Edge/Body ratio b-HAST Comparative 10.025 0.7 fail Inventive 1 0.050 0.9 pass

As the results of Table 1 indicate Inventive 1 has superior thicknessuniformity with a near equal thickness at the edges and the body. Theinventive example 1 also has superior results in accelerated reliabilitytest. The inventive example 1 suffers from an increase in ESR.

Test 3

A series of capacitors from Comparative 1 and Inventive 1 were separatedand subjected to 260° C. infrared heat treatment and to an oven heattreatment at 125° C., 150° C., and 175° C. for 2 hours. Under infraredheating conditions both samples demonstrated a slight increase in ESR.No obvious insulation layer was observed in cross-sectional views. Aseries of capacitors was also heated at 85° C. and 85% humidity at ratedvoltage and without voltage. ESR did not decrease.

Test 4

A series of capacitors from Comparative 1 and Inventive 1 were separatedand subjected to treatment at 121° C. and 85% relative humidity at ratedvoltage and under identical conditions without voltage. Inventive 1demonstrated a significant decrease in ESR from a mean of about 0.050Ohms to a mean of about 0.020 Ohms which is comparable to Comparative 1without the treatment. Furthermore, in subsequent dry heating at 125° C.for 24 hours leakage current after the treatment, both with and withoutvoltage, was stable and acceptable.

Test 5

A series of capacitors from Comparative 1 and Inventive 1 were prepared,with the exception that two layers of intrinsically conductive polymerwere applied sequentially. The samples were separated and subjected tomoist treatment at 121° C. and 85% relative humidity at rated voltageand under identical conditions without voltage. Inventive 1 demonstrateda significant decrease in ESR from a mean of about 0.050 Ohms to a meanof about 0.020 Ohms which is comparable to Comparative 1 without moisttreatment. In further processing the ESR remained stable post molding.The finished capacitors with encapsulation were tested for 21 hoursunder HAST condition. Leakage current was stable and acceptable. Incontrast, capacitors made from Comparative 1 showed severe increase inleakage current.

Another group of finished capacitors with encapsulation were passedthrough a Pb free SMT reflow with a peak temperature of 260° C. fivetimes. ESR was stable and acceptable. In comparison, capacitors madefrom Comparative 1 showed significant increase in ESR. Table 2 lists theESR values in Ohms for parts made from Comparative 1 and Inventive 1from different tests.

TABLE 2 Post End 5 Pass Post Sample molding of line Reflow b-HASTComparative 1 0.014 0.023 0.036 0.143 Inventive 1 0.011 0.014 0.0160.022

As realized from the examples, moist treatment of layers of anintrinsically conducting polymer over a primer, particularly a weakionic counterion, results in improved inter-layer adhesion. Subsequentheating even further improves the ultimate capacitor as evidenced byaging characteristics.

Test 6

A series of capacitors from Comparative 1 and Inventive 1 were separatedand subjected to treatment by dipping in glycerol for 5 mins followed bydrying at 130° C. for 30 mins. Inventive 1 demonstrated a significantdecrease in ESR from a mean of about 0.050 Ohms to a mean of about 0.026Ohms which is comparable to Comparative 1 without the treatment.

The invention has been described with reference to the preferredembodiments without limit thereto. One of skill in the art would realizeadditional embodiments and improvements which are within the meets andbounds of the invention as more specifically set forth in the claimsappended hereto.

1-22. (canceled)
 23. A process for forming a capacitor comprising:providing an anode comprising a dielectric thereon; applying a firstlayer of an intrinsically conducting polymer on said dielectric to forma capacitor precursor; applying at least one subsequent layer of anintrinsically conducting polymer on said first layer from a dispersionthereby forming a layered structure; fusing said layered structure by:swelling said layered structure with a liquid; and at least partiallyremoving said liquid.
 24. The process for forming a capacitor of claim23 wherein said swelling comprises dipping in said liquid.
 25. Theprocess for forming a capacitor of claim 23 wherein said swellingcomprises applying said liquid as a vapor.
 26. The process for forming acapacitor of claim 23 wherein said liquid is polar.
 27. The process forforming a capacitor of claim 26 wherein said liquid is selected from thegroup consisting of water, ethylene glycol, propylene glycol, glycerol,dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP) and N,N-dimethylformamide (DMF).
 28. The process for forming a capacitor ofclaim 23 wherein said removing of said liquid is by heating.
 29. Theprocess for forming a capacitor of claim 28 wherein said heating is at atemperature of at least 25° C. to no more than 150° C.
 30. The processfor forming a capacitor of claim 23 wherein said liquid is a solution.31. The process for forming a capacitor of claim 30 wherein saidsolution comprises a solvent.
 32. The process for forming a capacitor ofclaim 31 wherein said solvent is selected from the group consisting ofwater, alcohols, ketones, ethers and ring based polar solvents.
 33. Theprocess for forming a capacitor of claim 32 wherein said solvent isselected from the group consisting of water, ethanol, isopropanol,acetone, methyl ethyl ketone, dimethyl ether, diethyl ether andtetrahydrofurane.
 34. The process for forming a capacitor of claim 30wherein said solution comprises polyols.
 35. The process for forming acapacitor of claim 34 wherein said polyols are selected from the groupconsisting of sorbitol, mannitol, sucrose and lactose.
 36. The processfor forming a capacitor of claim 30 wherein said solution comprisesamino acids.
 37. The process for forming a capacitor of claim 36 whereinsaid amino acids are selected from the group consisting of glycine,alanine and lysine.
 38. The process for forming a capacitor of claim 23wherein said swelling is done by dipping or spraying.
 39. The processfor forming a capacitor of claim 23 wherein said at least partiallyremoving said liquid comprises at least one of reduced pressure orincreased temperature.
 40. The process for forming a capacitor of claim39 wherein said increased temperature is at least 25° C. to no more than150° C.
 41. The process for forming a capacitor of claim 23 furthercomprising applying a primer layer prior to said applying of said firstlayer of said intrinsically conducting polymer.
 42. The process forforming a capacitor of claim 41 wherein said primer layer comprises aweak ionic counterion.
 43. The process for forming a capacitor of claim42 wherein said weak counterion has a pKa of at least 0.25 to no morethan
 6. 44. The process for forming a capacitor of claim 43 wherein saidweak counterion has a pKa of at least 2.15 to no more than
 6. 45. Theprocess for forming a capacitor of claim 44 wherein said weak ioniccounterion comprises multiple carboxylic groups.
 46. The process forforming a capacitor of claim 45 wherein said weak ionic counterioncomprises 1 to 20 carbons.
 47. The process for forming a capacitor ofclaim 45 wherein said weak ionic counterion is selected from the groupconsisting of acetic acid, 1,2,3,4-butanetetracarboxylic acid, lysineand butanetetraacetic acid.
 48. The process for forming a capacitor ofclaim 41 wherein one of said intrinsically conducting polymer layer orsaid primer layer further comprises a cross-linker.
 49. The process forforming a capacitor of claim 48 wherein said cross-linker is an amine.50. The process for forming a capacitor of claim 49 wherein saidcross-linker is selected from diamine, triamine, oligoamine andderivatives thereof.
 51. The process for forming a capacitor of claim 41wherein said primer comprises dodecane diamine and1,2,3,4-butanetetracarboxylic acid.
 52. The process for forming acapacitor of claim 23 wherein said applying of said first layer of saidintrinsically conducting polymer comprises dipping into a dispersion ofsaid intrinsically conducting polymer.
 53. The process for forming acapacitor of claim 23 wherein said anode is a valve metal or conductiveoxides of said valve metal.
 54. The process for forming a capacitor ofclaim 23 wherein said intrinsically conducting polymer is selected fromthe group consisting of polyaniline, polythiophene and polypyrrole andtheir derivatives.
 55. The process for forming a capacitor of claim 23wherein said intrinsically conducting polymer is a polythiophene or aderivative thereof.
 56. The process for forming a capacitor of claim 55wherein said intrinsically conducting polymer is polymeric3,4-ethyledioxythiophene.
 57. A capacitor formed by the process of claim23.